In order to increase the breakdown voltage of a Schottky diode, a termination structure can be used to relax an electric field. As such a termination structure, a JTE (Junction Termination Extension), a FLR (Field Limiting Ring) (also referred to as “guard ring”), and the like have been known.
According to Jochen Hilsenbeck et al. “Avalanche Capability of Unipolar SiC Diodes: a Feature for Ruggedness and Reliability Improvement”. Material Science Forum. Vols. 615-617 (2009), pp. 659-662 (Non-Patent Document 1), a JTE is provided in a silicon carbide substrate. The JTE is covered with a passivation film (insulating film).
According to in In Ho Kang et al., “Post Annealing Etch Process for Improved Reverse Characteristics of 4H—SiC Diode”, Material Science Forum, Vols. 615-617 (2009), pp 663-666 (Non-Patent Document 2), an FLR is provided in a silicon carbide substrate. The FLR is covered with a thermal oxidation film (insulating film).